Method of incorporating photographic ingredients into photographic colloid compositions

ABSTRACT

A COLOR-COUPLING OR MASK-FORMING COMPOUND IS INHIBITED AGAINST DIFFUSION FROM THE LAYER OF A COLOR PHOTOGRAPHIC MATERIAL IN WHICH IS IN INCORPORATED BY MEANS OF A WATER-INSOLUBLE CHEMICALLY INERT WAX DISPERSED UNIFORMLY THROUGHOUT THE LAYER AND HAVING THE COLOR-COUPLING OR MASK-FORMING COMPOUND IN CONTACT THEREWITH, PREFERABLY CONTAINED IN FINELY DIVIDED PARTICLES THEREOF. ANY OF A VARIETY OF NATURAL OR SYNTHETIC WAXES CAN BE EMPLOYED , PREFERABLY HAVING A LOW REFRACTIVE INDEX, AND THE WAX AND THE COLOR-COUPLING OR MASK-FORMING COMPOUND CAN BE INCORPORATED INTO THE LAYER-FORMING COMPOSITION IN A VARIETY OF WAYS.

3,676,142 Patented July 11, 1972 ha e 3,676,142 METHOD OF INCORPORATING PHOTOGRAPI HC INGREDIENTS INTO PHOTOGRAPHIC COLLOID COMPOSITIONS Jan Albert Carpentier, Walem, and Alfons Jozef De Pauw, Edegem, Belgium, assignors to Agfa-Gevaert, Mortsel, Belgium No Drawing. Filed Sept. 10, 1969, Ser. No. 856,825 Claims priority, application Great Britain, Sept. 10, 1968, 43,029/68 Int. Cl. B01j 13/00; G03c .Z/40, N72

US. Cl. 96-100 (Ilaims ABSTRACT OF THE DISCLOSURE This invention relates to hydrophilic colloid compositions comprising a hydrophilic colloid and uniformly distributed therethrough particles of a wax containing colour coupler and/or mask-former, to light-sensitive emulsions comprising silver halide dispersed in such hydrophilic colloid compositions and to methods of preparing said hydrophilic colloid compositions and lightsensitive emulsions.

By colour coupler is meant any component which in silver halide photography couples with an oxidised aromatic primary amino colour developing agent to form a dye image. By mask-former is meant a component which oxidatively couples with a colour coupler in an oxidizing bleaching bath as described for example in United Kingdom patent specifications 880,865 and 975,- 932 to form a coloured mask image.

In the preparation of photographic silver halide emulsions it is often necessary to incorporate therein colour coupling and/or mask-forming components. Some of the most useful types of colour couplers and mask formers are those which are provided, in order to render them nondifiusible in hydrophilic colloid media, with one or more ballast groups, e.g. a long chain aliphatic group such as an alkyl group of from 5 to 20 carbon atoms. The presence of this ballast group imparts to the molecule a hydrophobic character so that these non-diffusible ingredients must also be provided in the course of their synthesis with one or more salt-forming groups i.e. carboxy and/ or sulpho groups, which in the form of their alkali metal salts provide the ingredients with watersoluble groups of hydrophilic character so that said ingredients can still be incorporated from aqueous solutions in aqueous hydrophilic colloid compositions.

However, the incorporation of these non-diffusible colour couplers and mask-formers containing salt-forming groups, into aqueous hydrophilic colloid compositions frequently still possess a number of difiiculties. Indeed, certain of the above components carrying sulpho and/or carboxyl groups are not soluble enough, i.e. in the concentration desired, in alkaline solutions while others crystallize after some time in said solutions or give rise to flocculation when incorporating the ingredient solution in the aqueous hydrophilic colloid medium. Moreover, some compounds are soluble only in highly alkaline solutions which are too basic for use as such in conventional light-sensitive silver halide material, where approximately neutral solutions are most desirable; when highly alkaline solutions are used the hydrophilic colloid composition should be reacidified afterwards whereby fiocculation might occur. Further, some of the compounds carrying water-solubilizing groups, though they possess ballast groups, still have the tendency to wander from the emulsions in which they have been incorporated.

Other attempts have been made to avoid diifusion of colour couplers and mask-formers in hydrophilic colloid media according to which wandering of said compounds is prevented or retarded by associating them in the said hydrophilic colloid with a water-insoluble cellulose derivative or with a water-insoluble natural or artificial resin or gum. It was found, however, that when colour couplers are associated with water-inso1uble cellulose derivatives, resins or gums it is sometimes difficult to obtain satisfactory dye densities on colour development because the processing baths do not act to a sufiicient extent or sufiiciently rapidly upon the colour couplers whereby it is necessary to incorporate in the said water-insoluble materials high-boiling solvents known as porosity-modifiers which improve the porosity i.e. the permeability of the particles of cellulose derivative, gum or resin to the processing solutions permitting more easy and rapid penetration of the processing solutions.

It has now been found that when in a hydrophilic colloid layer of a photographic colour material the colour couplers and/ or mask-formers are associated with a water-insoluble wax, the said colour couplers and maskformers have an improved fastness to diffusion and are sufficiently accessible to the developing and other processing solutions to enable the usual methods of processing to be applied.

Thus, in accordance with the present invention there are provided stable homogeneously divided dispersions in hydrophilic substantially transparent colloid carriers such as gelatin, polyvinyl alcohol and the like of discrete particles of a water-insoluble chemically inert wax containing a colour coupling and/or mask-forming component.

The invention, therefore, includes emulsions of lightsensitive silver halide in a hydrophilic colloid binder such as gelatin having distributed therethrough discrete particles of a water-insoluble wax containing colour coupler and/or mask-former; it also includes a lightsensitive material comprising at least one silver halide emulsion layer containing uniformly distributed in the hydrophilic colloid binder of said layer particles of a water-insoluble wax containing colour coupler and/or mask-former.

The present invention further provides a method of forming a hydrophilic colloid composition which comprises a hydrophilic colloid binder and uniformly distributed therethrough a colour coupling and/or maskforming component, wherein the said component(s) is- (are) dispersed into the said hydrophilic colloid composition in the presence of a water-insoluble chemically inert wax.

The method of the invention is generally carried out by the steps of mixing the colour coupling and/ or maskforrning component with a water-insoluble wax and dispersing the said mixture in the said hydrophilic colloid composition. Mixing of the colour coupler and/or maskformer with the water-insoluble wax usually occurs by forming a liquid composition of said component and said wax with the aid of an organic solvent or mixture of organic solvents, dispersing or emulsifying the liquid composition formed in extremely fine droplets in a hydrophilic colloid composition in liquid state preferably in the presence of a dispersing agent, and if necessary removing substantially all of the said solvent or mixture of solvents leaving thereby particles of said water-insoluble wax containing said component, uniformly distributed in the hydrophilic colloid composition.

All water-insoluble thermoplastic wax-like materials of the known six classes of Waxes i.e. vegetable waxes, insect waxes, animal waxes, mineral waxes, petroleum waxes and synthetic waxes, as well as the water-insoluble wax-like components that occur individually in said waxes, more particularly long-chain hydrocarbons, fatty saturated and unbr-anched acids and alcohols, as well as the ethers and esters of substantially aliphatic monohydric alcohols, can be used for the purpose of the invention.

The petroleum waxes are compositions consisting mainly of a mixture of long-chain hydrocarbons whereas the vegetable, animal, insect and mineral waxes are usually compositions made up largely of esters formed in nature by the union of higher alcohols with the higher fatty acids, for example, carnauba wax, wool wax and montan wax. Associated with these esters are one or more of the following components which vary greatly in amount in accordance with the source of the wax: free saturated and unbranched fatty acids and monohydric alcohols and long-chain hydrocarbons, to mention the most important.

In general, the wax-like materials according to the invention are meltable, thermoplastic materials which are mostly opaque in solid state and have properties closely resembling those of beeswax. They dilfer from related natural and synthetic products such as oils, fats, gums and resins amongst others in that they are transferred from the solid to the liquid state at temperatures comprised generally between 20 and 100 C. (in some extraordinary cases up to 200 C., which applies particularly to some synthetic waxes) and that they have a low melt viscosity.

The following is a non-limitative list of water-insoluble 'waxes and wax-like materials suitable for use in accordance with the present invention:

(A) Vegetable waxes carnauba wax ouricury wax candelilla wax sugarcane wax Japan wax (B) Animal Waxes spermacetic wax wool wax (C) 'Insect waxes beeswax shellac wax Chinese insect wax (D) Petroleum waxes 4 (E) Mineral waxes ozocerit wax peat wax ceresin montan wax Utah wax F) Synthetic waxes or wax-like materials 1) Wax-like components that occur individually in natural waxes more particularly:

(a) the wax-like fatty saturated alcoholszhexadecyl alcohol and octadecyl alcohol and mixtures thereof such as lanetta wax;

(b) the wax-like straight-chain saturated fatty acids of the formula C H COOH wherein n is an integer of at least 11, particularly myristic, palmitic and stearic acid; 1

(c) synthetic esters derived from fatty acids and fatty alcohols which are of the natural wax esters type:

cetyl palitate stearyl stearate cetyl myristate.

(2) Other synthetic esters derived from fatty acids such as:

the wax-like esters sold under the trade name Glyco Wax S 932 by Glyco Chemicals Inc., New York, N.Y., U.S.A.,

pentaerythritol esters of fatty acids e.g. of stearic acid, palmitic acid and lauric acid such as Pe-Tetrastearate (trade name for a pentaerythritol ester of stearic acid of Hercules Powder Co. Inc., Wilmington, Del., U.S.AJ,

alkyl esters of 12-hydroxy-stearic acid such as octadecyl- .ll-hydroxystearate,

sucrose diesters of fatty acids such as sucrose distearate marketed under the trade name SES2, T-l by Sucrose Chemical Division of Colonial Sugars Company, Gramercy, La., U.S.A.,

esters of fatty acids and hexitol anhydrides derived from sorbitol such as sorbitan monostearate marketed under the trade names Span 60 and Arlacel 60 by Atlas Refining Co., Wilmington, Del., U .S.A.

(3) Synthetic parafiin waxes e.g. those known as the Fisher-Tropsch waxes which are long-chain aliphatic hydrocarbons.

1(4) The hydrogenated oils e.g. hydrogenated castor oil and sperm oil such as Castorwax (trade name for hydrogenated castor oil of the Baker Caster Oil Co., Bayonne, N.I., USA.) and Spermafol 52 (trade name for hydrogenated sperm oil of Archer Daniel Midland Co., Minneapolis, Minn., U.S.A.).

[(5) Chemically modified natural waxes amongst which:

(a) the halogenated hydrocarbons such as chlorinated parafiins;

(b) the partly oxidised paraffins;

(c) montan wax derivatives such as the Hoechst waxes formerly known as I.G.-waxes or Gersthofen waxes which are generally glycerol, glycol, or polymerised ethylene glycol esters of acids from montan Wax.

(6) Amide derivatives of fatty acids eg stearamide such as Goudamide-S (trade name for stearamide of Gouda-Apollo N.V., Gouda, Netherlands), the waxes sold under the trade names Ceramid and Acrawax by Glyco Chemicals Inc., New York, N.Y., USA. for stearic acid monoethanolamide and for the reaction product of hydrogenated castor oil with monoethanolamine re spectively, the Carlisle Waxes (trade name of Carlisle Chemical Works, Reading, Ohio, USA. for amide waxes) such as Carlisle 280 Wax (trade name for N,N-ethylenebis-stearamide) and Carlisle 400 Wax (trade name for a N,N-alkylene-bis fatty acid amide).

For more details about water-insoluble waxes and waxlike thermoplastic materials there can be referred to The Chemistry and Technology of Waxes, by A. H. Warth, 2nd ed., 1956, Reinhold Publishing Corporation, New York, USA. and to Industrial Waxes, vol. I, by H. Bennett, 1963, Chemical Publishing Company Inc., New York, USA.

As a guide in choosing suitable waxes for use according to the present invention, the requirements will now be given which said materials should fulfil to give the best results.

The waxes should of course be chemically inert toward the photographic emulsion ingredients, the photographic colloid, the photographic processing baths, etc. For the purpose of the invention they should not adversely affect the light-sensitivity or developa-bility of the silver halide nor give rise to fogging. They should preferably have a sufiiciently low refractive index to enable the discrete particles of wax containing colour coupler and/ or mask-former to have approximately the same index of refraction as the hydrophilic colloid materials employed as binder for the silver halide, thereby minimizing the opacity or light-scattering of the emulsion coating.

It will be apparent that it may not be possible to find a single wax which simultaneously fulfils all the requirements given above to the maximum extent. It may, therefore, be necessary to reconcile one property of the material with another. In general that wax is chosen which possesses the most adequate combination of properties.

It is sometimes advantageous to employ a mixture of two or more waxes in the same dispersion in order to obtain the desired combination of properties. For instance a certain amount of beeswax or carnauba wax can be mixed with low-melting paraffin wax to raise the melting point of the paraffin wax. Another example is the addition of ozocerite wax which is soft and plastic to a parafiin wax of approximately the same melting point which is hard and lacks plasticity. Further it may be desirable to use a mixture of waxes in the correct proportions to obtain the desired refractive index. Thus, it is possible to use so-called blended waxes which are generally mixtures of hydrocarbon waxes, mixtures of petroleum waxes with natural Waxes or mixtures of hydrocarbon waxes with synthetic waxes.

When we use the term water-insoluble Wax, therefore, we do not necessarily mean a single compound but include a mixture of two or more compounds.

\In the method of the invention for preparing dispersions in a hydrophilic colloid medium of particles composed of wax and colour coupling or mask-forming component, a liquid composition is prepared of both the wax and the said component, which liquid composition is dispersed in the said hydrophilic colloid medium whereupon the mixture of wax and component is precipitated in the hydrophilic colloid medium.

A most convenient way of dispersing such particles of wax and colour coupler or mask-former in a hydrophilic colloid medium is to make up a liquid solution of the wax and the colour coupler or mask-forming component in a common organic solvent or mixture of organic solvents and to disperse the solution formed in the said hydrophilic colloid medium whereupon a mixture of the Wax with the component(s) can be precipitated in the hydrophilic colloid medium by removal of the solvents employed. The organic solvents or mixture of organic solvents employed in this connection are thus characterized by being solvents for both types of substances thereby inducing mutual miscibility of the colour coupler or mask-former and the wax.

A variety of methods may be employed for preparing the liquid solutions of the wax plus the colour coupler or mask-former in common organic solvents or mixtures of organic solvents.

According to one procedure, the colour coupling or mask-forming component and the water-insoluble wax are dissolved in a common water-immiscible or sparingly water-miscible solvent or a mixture of such solvents. It is also possible to dissolve both the said wax and component in a completely water-miscible solvent or a mixture of such solvents. Alternatively, the said wax and the said component can be dissolved in a mixture of at least one completely water-miscible solvent and at least one waterimmiscible or sparingly water-miscible solvent.

Thus the solvent materials, employed for making the liquid solution of wax and colour coupler or mask-former include high-boiling as well as low-boiling water-miscible solvents e.g. methanol, ethanol, isopropyl alcohol, dimethyl sulphoxide, tetrahydrofuran, N-methylpyrrolidone, dioxan, acetone, butyrolacetone, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, glycerol, acetonitrile, formamide, dimethyl formamide, diacetone alcohol, 1,1-tetrahydrothiophene dioxide, dimethoxyethane, etc. as well as sparingly water-miscible or water-immiscible solvents preferably having a boiling point of at most 150 C. e.g. methylene chloride, methyl formate, ethyl formate, n-butyl formate, methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, butyl acetate, methyl propionate, ethyl propionate, carbon tetrachloride, sym.-dichloroethane, trichloroethylene, 1,2-dichloropropane, chloroform, amyl chloride, methyl ethyl ketone, diethyl ketone, methyl n-propyl ketone, diisopropyl ether, cyclohexane, methyl cyclohexane, ligroin (boiling range: -110" C.), benzene, toluene, xylene nitromethane, etc. and mixtures of water-miscible solvents with water-immiscible or sparingly Water-miscible solvents.

Of course, in the above methods of forming a liquid solution of wax and colour coupling or mask-forming component the said components need not necessarily be dissolved together in a solvent or mixture of solvents; it is possible to dissolve them separately in a solvent or mixture of solvents and then to admix the solutions obtained, the solvents or solvent partners used in the preparation of the separate solutions being in practice preferably the same for both solutions. Thus when there is referred to forming a liquid solution of the wax and the colour coupler or mask-former there is included that the said wax and the said colour coupler and mask-former are dissolved separately although this procedure is not so much to be recommended because it unnecessarily complicates the formation of the liquid solution of wax and component.

The solvent or solvent partners (in the case of mixtures of solvents) employed according to the present invention for dissolving the mask-forming or colour coupling component and the wax are chosen in such a way that the said component and the said wax dissolve completely with the required concentration.

It may sometimes be necessary in order to facilitate dissolution of the component to effect the formation of said liquid solution in the presence of a little water or an alkali-solution and/ or a wetting agent. For instance in those cases where the wax and the component are dissolved in water-immiscible or sparingly water-miscible solvents or mixtures of such solvents with completely water-miscible solvents difiiculties are sometimes encountered in that the said component, probably owing to the presence of water-solubilizing sulpho and/or carboxyl groups in acid or salt form, dissolve rather difficultly. In these cases, dissolution of such like components can be improved by dissolving the wax and the components in the presence of some water or an alkali solution, optionally also in the presence of a wetting agent. Water is used when the components are in neutral form, i.e. when they contain sulpho and/ or carboxyl groups in salt form whereas alkali is used when the said components are in acid form i.e. when they contain sulpho and/ or carboxyl groups in acid form; the amount of alkali can be limited to that necessary for neutralizing the acid groups. Alternatively, the wax can be dissolved separately in the water-immiscible or sparingly water-miscible solvent(s) or mixtures thereof with completely water-miscible solvents whereupon the solution formed is admixed with the solution of the colour coupling or mask-forming component formed as described above.

Though in the method of the invention for obtaining hydrophilic colloid media having dispersed therein particles of a water-insoluble wax containing colour-coupling and/or mask-forming component, the most convenient way of dispersing such particles in the hydrophilic colloid is to make up as described above a solution of the wax and the said component in a suitable organic solvent or mixture of organic solvents and then to disperse said solution in the hydrophilic colloid composition, this procedure might give unsatisfactory results in those cases where more or less Water-soluble components are involved in that when dispersing the organic solution of wax and component into an aqueous solution of hydrophilic colloid the said component tends to leave the organic solution and diffuse into the aqueous phase thereby reducing the amount of component that is in admixture with the wax upon removal of the solvents from the hydrophilic colloid composition.

A convenient way of dispersing in hydrophilic colloid media components that might give rise to the above unsatisfactory results when dispersed according to one of the methods described hereinbefore and according to which dispersions are obtained in hydrophilic colloid media of particles of wax encasing or surrounding the said component thereby minimizing the tendency of the component to diffuse into the aqueous hydrophilic colloid composition comprises the steps of forming a solution in aqueous medium of the colour coupling or mask-forming component, dispersing the aqueous solution formed in a solution of the wax in a water-immiscible or sparingly water-miscible solvent or mixture of such solvents, dispersing the resulting liquid composition of wax and component in the hydrophilic colloid composition and removing substantially all of the water-immiscible solvent(s).

The latter method of dispersing wax plus component in hydrophilic colloid media can be used whenever the components are soluble in aqueous medium, optionally in the presence of alkali and/ or a water-miscible solvent and is therefore not limited to cases where components that are quite water-soluble are intended to be dispersed in hydrophilic colloid media.

Having now described in detail various methods that can be applied for forming a liquid composition of the wax and the colour coupling or mask-forming component there will now be described detailedly how the said liquid composition of wax and component is incorporated into photographic light-sensitive silver halide emulsions.

In accordance with the present invention a liquid composition of the water-insoluble wax plus the component e.g. prepared according to one of the methods described above is added to a hydrophilic colloid composition in liquid state e.g. an aqueous solution of gelatin, a melted silver halide emulsion, etc. and highly dispersed therein by mechanical means. In this way, in the hydrophilic col loid composition a very fine dispersion is obtained of discrete particles comprising water-insoluble wax and colour coupling or mask-forming component(s). The dispersion may be effected with the aid of a homogemzer, a colloid mill, an ultrasonic wave generator or the like, preferably in the presence of surface active agents.

In making the liquid composition of the component and the wax in the solvent or mixture of solvents the amount of wax is dependent on the amount of component used. The wax is generally used in amounts from 25 mg. to 3 g., preferably from 250 mg. to 1.5 g. relative to l g. of component. The amount of liquid composition of component and wax which is admixed with the hydrophilic colloid composition may vary within very wide limits; it S actually pendent on the concentration of the said component in the said liquid composition and on the concentration desired of the component in the colloid composition. In general about 1 volume of liquid composition is admixed with 1 to 20 volumes of hydrophilic colloid composition.

The hydrophilic colloid composition into which the liquid composition of the component(s) and the wax has been dispersed may be a light-sensitive silver halide emulsion which is then coated as such whereupon the solvents are removed as described hereinafter or coated after being previously subjected to a treatment as described hereinafter to remove the solvents employed. However, it has been experienced that it is advantageous to first disperse with efiicient agitation the liquid composition of the component(s) and the said Wax in an aqueous solution or melted gel of a non-light-sensitive hydrophilic colloid e.g. a mere aqueous solution of gelatin. The resultant dispersion, preferably after removal of the solvent(s) or substantially all of the solvent(s) employed, can be stored (preferably in gelled state) for weeks and then mixed with the light-sensitive silver halide emulsion at the appropriate moment.

The use of a thus pre-fabricated dispersion is preferred because it avoids excessive agitation of the light-sensitive silver halide emulsion, which could cause fog, and in this way the already finely divided colour couplers or maskformers can be homogeneously incorporated in the silver halide emulsion Without a special stirring technique.

The use of the prefabricated dispersion offers an excellent reproducibility since it is possible to incorporate the colour couplers or mask-formers into the photographic light-sensitive emulsion always in the same concentration and with the same degree of dispersion. By the use of the prefabricated dispersion, the solvents used in making the liquid composition of the colour coupler or mask-former and wax that could be harmful to the photographic emulsion are never in contact therewith because they are removed from the colloid medium containing the dispersed colour coupler or mask-former before the latter is incorporated into the emulsion.

The solvent(s) employed in making the liquid composition of the wax and the component is (are) preferably removed during and/ or after the mixing step of the said liquid composition with the hydrophilic colloid composition. This removal is generally effected by evaporation from said composition occasionally by applying reduced pressure generally from 500 mm. to 10 mm. Hg and/or moderate heating preferably not higher than C. Water-miscible solvents having too high a boiling point to be easily removed by evaporation under reduced pressure are removed, unless they are photographically inert, by washing the gelled and noodled colloid composition.

It is also possible to remove the solvents from the lightsensitive silver halide emulsion into which the component has been incorporated by evaporation on drying of the coated emulsion composition; the latter is effected by allowing the solvent or solvents to escape by evaporation on drying the coated emulsion which is only applicable when sufliciently volatile solvents are used. Of course, in case the organic liquid composition of the said component and the wax has first been admixed with a mere aqueous solution of hydrophilic colloid, as explained above, the composition formed can be stored without removal of the solvents.

The use of a little surface-active agent facilitates the dispersion of the organic liquid composition of component and wax into the hydrophilic colloid composition. This surface active agent can be added already at the step of making the liquid composition of the said component and wax.

The surface-active agents used may be of the ionic, nonionic or amphoteric type. Examples of suitable ionic sur face active agents are: the sodium salt of oleyl tauride, sodium stearate, heptadecenyl-benzimidazole sulphonic acid sodium salt, sodium sulphonates of higher aliphatic alcohols, e.g. Z-methylhexanol sodium sulphonate; sodium di-iso-octyl-sulphosuccinate, sodium dodecyl sulphate and dodecylbenzene sulphonic acid sodium salt. Examples of suitable non-ionic emulsifying agents are saponine, condensation products of alkyl phenols and ethylene oxide, e.g. octylphenyl polyglycol ether, isononylphenoxypoly- (ethylenoxy) ethanol and polyethylene glycol oleate.

A survey of emulsifying agents and wetting agents, representatives of which can be used in the method of the present invention are described by Gerhard Gawalek Waschund Netzmittel, Akademieverlag, Berlin (1962).

Although in applying the method according to the present invention the use of gelatin as hydrophilic colloid is favoured, other water-soluble colloidal materials or mixtures of them can be used too, e.g. colloidal albumin, zein, casein, a cellulose derivative such as carboxymethyl cellulose, a synthetic hydrophilic colloid such as polyvinyl alcohol, poly-N-vinyl pyrrolidone, etc.

The method of the invention has proved to be particularly valuable for the incorporation of hydrophobic colour couplers or mask-formers that are difficultly water-soluble or soluble only in highly alkaline solution.

It will be appreciated however, that the method of the invention is also suitable for the introduction into photographic hydrophilic colloid compositions of water-soluble colour couplers and mask-formers for which preferably special precautions should be taken as described above.

According to the method of the present invention the hydrophilic colloid layers formed upon drying are very clear and colourless. Very good and extremely fine dispersions of the colour coupler or mask-former in the hydrophilic colloid composition are obtained.

It is further possible to obtain an intimate mixing in the desired and exact ratio of a colour coupler and a maskforming compound, which oxidatively couples in the pho tographic bleaching bath with the colour coupler according to the process of preparing colour-corrected photographic colour images as described, e.g. in our United Kingdom patent specifications 880,862 and 975,932. The colour coupler and mask-forming compound are intimately mixed with each other and are present in exact and always the same ratio throughout the entire emulsion layer.

.Another advantage is that it is possible to incorporate the components in their neutral form that is, it is not necessary to form components with salt forming groups in order to facilitate the incorporation of said components. Moreover, interaction of the component with the hydrophilic colloid such as gelatin can be avoided so that no raise in viscosity takes place as is otherwise sometimes the case.

By the presence of water-insoluble wax the said components are less liable to diifusion. This is true even when the components are quite alkali-soluble. This means that the protection afforded by the water-insoluble wax for the components, provides particles which are protected against the surrounding aqueous phase, against the influence of other emulsion ingredients such as softening agents, hardening agents, etc., against hydrolysis and crystallization. Moreover, in the case of photographic material for tropical use the components that are in admixture with the wax are shielded against moist atmosphere.

Although the waxes prevent the diffusion of the components into adjacent water-permeable layers said components are sufiiciently accessible to the developing and other processing solutions to enable the usual methods of processing to be applied. This is proved by the high colour densities obtained on colour development of emulsion layers comprising colour couplers incorporated "according to the method of the invention.

When colour couplers are dispersed in photographic emulsions according to the present invention the dyes formed therewith on colour development not only show a very high colour density but also have an improved stability against light and moisture and their tendency for aggregation and/r crystallization is avoided or reduced; this elfect leads to improvement in the spectral absorption characteristics of the dye image. Moreover, it has been 10 found that in addition to the above advantages a number of waxes have the valuable property of conferring a slight increase in the sensitivity of the photographic material and also the valuable property of causing a shift in the absorption maximum of the dyes formed on colour development. The following examples illustrate the present invention.

EXAMPLE 1 1 g. of the cyan-forming colour coupler having the following structural formula:

and 1 g. of Japan wax are dissolved at about 50 C. in 5 ml. of ethyl acetate.

The solution obtained is dispersed by means of a homogenizer in 20 ml. of a 5% aqueous solution of gelatin in the presence of 0.5 ml. of a 25% aqueous solution of dodecylbenzene sulphonic acid sodium salt as dispersing agent.

After having made the dispersion, a vacuum of 400 mm. Hg at a temperature of 60 C. is applied to the composition, whilst it is slowly stirred.

The composition from which the ethyl acetate has been removed is then admixed at 38 C. with 50 g. of a red-sensitized silver bromo-iodide emulsion comprising per kg. 0.33 mole of silver halide and 65 g. of gelatin.

The colour emulsion obtained is coated and dried in the usual manner.

Upon exposure and development by means of a conventional aromatic primary amino colour developing agent an intense cyan dye image is obtained.

EXAMPLE 2 Example 1 is repeated with the difference that now 0.5 g. of spermacetic Wax is used instead of 1 g. of Japan wax and that chloroform is used as solvent.

Moreover the solution of spermacetic Wax and colour coupler in chloroform is now dispersed directly in 50 g. of the said red-sensitized silver bromo-iodide emulsion in the presence of 0.5 ml. of a 25 aqueous solution of dodecylbenzene sulphonic acid sodium salt as dispersing agent, whereupon the chloroform is removed by applying a reduced pressure of 400 mm. Hg at 60 C. with stirring.

An intense cyan dye image is obtained upon exposure and colour development in the conventional manner.

EXAMPLE 3 1 g. of the yellow-forming colour coupler having the following structural formula:

and 0.5 g. of Glycowax S 932 (trade name) are dissolved at about 50 C. in 5 ml. of tetrahydrofuran.

The solution obtained is dispersed by means of a high speed mixer into 20 ml. of a 5% aqueous solution of gelatin comprising 0.5 ml. of a 25% aqueous solution of dodecylbenzene sulphonic acid sodium salt as wetting agent.

The colloid composition is cooled and the gel obtained noodled and washed with cold water to remove the tetrahydrofuran. The noodles are remelted at 40 C. and the melt added in the dark to 45 g. of a blue-sensitive silver halide emulsion. The emulsion is coated in the usual way as an emulsion layer of a conventional multilayer colour material.

1 1 EXAMPLE 4 having so N a :0 N a and 0.5 g. of lanetta wax are dissolved at 5560 C. in a mixture of ml. of ethyl acetate and 2 ml. of ethanol in the presence of 0.5 ml. of polyethylene glycol oleate as wetting agent.

The solution formed is dispersed by means of an ultrasonic wave generator in 45 g. of a green-sensitized fine grain silver chlorobromide emulsion, which comprises 0.5 ml. of a 25% aqueous solution of dodecylbenzene sulphonic acid sodium salt as dispersing agent, at a temperature of 37 C.

After having made the dispersion of colour coupler plus lanetta wax in the emulsion a vacuum of 1502OO mm. Hg at a temperature of 37-40 C. is applied While slowly stirring.

The usual additives are incorporated into the emulsion such as hardeners, stabilizers, etc., whereupon the emulsion is coated and dried in a conventional manner.

Upon exposure through a step wedge and colour development by means of a conventional colour developing bath, an intense magenta wedge image is obtained.-

EXAMPLES 5-7 Example 4 is repeated with the difference that instead of lanetta Wax once beeswax is used, another time Glycowax S 932 (trade name) and still another time Span 60 (trade name) and with the difference that the solution of wax and colour coupler in ethyl acetate and ethanol is first dispersed into ml. of a 5% aqueous solution of gelatin comprising 0.5 ml. of a aqueous solution of dodecylbenzene sulphonic acid sodium salt whereupon the solvents are removed by evaporation under reduced pressure and the resulting gelatin composition is admixed with 45 g. of the said green-sensitized silver halide emulsion.

EXAMPLE 8 1 g. of the yellow-forming colour coupler having the following structural formula:

OOH

and 0.5 g. of Spermafol 52 (trade name) are dissolved by heating in 5 ml. of ethyl acetate.

The solution obtained is dispersed by means of a homogenizer into 20 ml. of a 5% aqueous gelatin solution comprising 0.5 ml. of a 25% aqueous solution of dodecylbenzene sulphonic acid sodium salt.

The ethyl acetate is removed from the gelatin composition by evaporation under reduced pressure (250-400 mm. Hg) and heat (60 C.).

The resulting composition comprising dispersed therein colour coupler and Wax is admixed with a conventional blue-sensitive gelatino silver halide emulsion at 38 C. The silver halide emulsion is then coated on a conventional support and dried.

Upon exposure and colour development a yellow image is obtained.

In the same way as described above, the yellow forming colour coupler was incorporated into a silver halide emulsion using as wax stearic acid instead of Spermafol 52 (trade name).

EXAMPLE 9 l g. of the magennta-forming couour coupler having the following structural formula:

and 1 g. of Japan wax are dissolved at C. in 8 ml. of tetrahydrothiophen-l:l-dioxide. The solution formed is dispersed by means of an ultrasonic wave generator to a melted gel at 40 C. of: 1 g. of gelatin, 20 ml. of water and 0.5 ml. of a 25 aqueous solution of dodecylbenzene sulphonic acid sodium salt.

The colloid composition is allowed to cool and the gel obtained is noodled and washed with cold water to remove the solvent. The noodles are remelted at 40 C. and the melt added in the dark to 40 g. of a green-sensitized silver halide emulsion. The emulsion is coated in the usual manner and dried.

EXAMPLE 10 Six solutions are prepared of 1 g. of the cyan-forming colour coupler having the following structural formula:

and 0.5 g. of one of the following waxes: white beeswax, Glycowax S 932 (trade name), Parafiin 136-138, Castor Wax (trade name), Pe-Tetrastearate (trade name) and Span 60 (trade name) by dissolving the wax selected and the colour coupler at 60 C. in 5 ml. of ethyl acetate.

The six solutions are then separately dispersed in 20 ml. of 5% aqueous gelatin in the presence of 0.5 ml. of a 25% aqueous solution of dodecylbenzene sulphonic acid sodium salt.

The ethyl acetate is removed from the colloid compositions by evaporation under reduced pressure (250-400 mm. Hg) at 60 C.

The resulting compositions comprising dispersed therein colour coupler and wax are mixed at 38 C. with 50 g. of a red-sensitized silver bromoiodide emulsion comprising per kg. 0.33 mole of silver halide and 65 g. of gelatin.

The colour emulsions obtained were coated in the usual manner and dried.

After exposure through a step Wedge and conventional colour processing cyan coloured Wedge images are obtained of which those obtained in the presence of beeswax, Span 60 (trade name) and Glycowax S 932 (trade name) excel by their deep cyan colour.

13 EXAMPLE 11 1 g. of the magenta-forming colour coupler having the following structural formula:

(iJHa-C Fa O CH CH 2)15 a SOaNa and 0.25 g. of Carlisle 400 Wax (trade name) are dissolved at 80 C. in 5 ml. of N-methyl-Z-pyrrolidinone. The solution obtained is dispersed by means of a highspeed stirrer at 40 C. into 20 ml. of 5% aqueous gelatin containing 0.5 ml. of a 25% aqueous solution of dodecylbenzene sulphonic acid sodium salt.

The gelatin composition thus obtained can be stored in gelled state for weeks and then added to a conventional silver halide emulsion.

Before addition to a conventional green-sensitized silver halide emulsion the gelled gelatin composition is noodled and washed with cold water to remove the N- methyl-Z-pyrrolidinone.

EXAMPLE 12 1 g. of the yellow-forming colour coupler having the following structural formula:

I S OsNa and 0.5 g. of vaselin (petrolatum wax) are dissolved in a mixture of 4 ml. of ethyl acetate and 1 ml. of ethanol in the presence of 1 ml. of water.

The solution formed is dispersed by means of a high speed stirrer into 30 ml. of a 5% aqueous solution of gelatin in the presence of 0.5 ml. of a 25 aqueous solution of dodecylbenzene sulphonic acid sodium salt.

In order to remove the ethyl acetate from the gelatin composition the latter is heated at 60 C., under reduced pressure (250-400 mm. Hg).

The resulting gelatin composition comprising dispersed therein colour coupler and the above wax is admixed at 38 C. with 30 g. of a conventional blue-sensitive silver halide emulsion which is then coated and dried in the usual manner.

Upon exposure and colour processing a yellow dye image is obtained.

In a similar way as described above, the colour coupler was incorporated into a silver halide emulsion using as wax sucrose distearate and spermacetic wax instead of vaselin.

EXAMPLE l3 1 g. of yellow-forming colour coupler having the following structural formula:

O-(OH2) 15-011;

After the removal of the ethyl acetate by heating at 60 C. under reduced pressure the gelatin composition was admixed at 40 C. with a conventional blue-sensitive silver halide emulsion.

The emulsion is coated in the usual manner and dried.

EXAMPLE 14 Example 13 is repeated with the difference that now 0.5 g. of SES-2, T-l (trade name) is used instead of Goudamide S (trade name) and that the solution is dispersed directly into a melted blue-sensitive gelatino silver halide emulsion from which the ethyl acetate is removed by applying a vacuum of about 250 mm. Hg at 40 C.

EXAMPLE 15 1 g. of cyan-forming colour coupler having the following structural formula:

and 0.5 g. of ozocerit wax are dissolved in 5 ml. of chloroform.

The solution is then dispersed into a red-sensitized silver halide emulsion as described in Example 2 and the emulsion further treated as in said example.

EXAMPLE 16 1 g. of the cyan-forming colour coupler of Example 15 and 0.5 g. of Ceramid (trade name) are dissolved in 5 ml. of ethyl acetate.

The ethyl acetate solution was then dispersed into a gelatin solution as described in Example 1. The gelatin composition is further treated as described in said example EXAMPLE 17 1 g. of the magenta-forming colour coupler of Example 4 and 0.5 g. of Goudamide S (trade name) are dissolved in 5 ml. of ethyl acetate in the presence of 0.5 ml. of water and 0.5 ml. of polyethylene glycol oleate.

The resulting solution is dispersed by means of a highspeed mixer into 30 ml. of a 5% aqueous gelatin solution comprising 0.5 ml. of a 0.25% aqueous solution of dodecylbenzene sulphonic acid sodium salt.

After having made the dispersion, a vacuum of 400 mm. Hg at a temperature of 60 C. is applied to the composition whilst slowly stirring.

The composition from which the ethyl acetate has been removed is then admixed at 38 C. with 45 g. of a greensensitized silver halide emulsion. The emulsion is coated and dried in the usual way.

Upon exposure through a step wedge and colour processing in the conventional way an intense magenta coloured wedge image is formed.

In a similar way as described above, the colour coupler was incorporated into a green-sensitized silver halide emulsion together with Japan wax and spermacetic wax as wax instead of Goudamide S.

EXAMPLE 18 l g. of the yellow-forming colour coupler having the following structural formula:

is dissolved in 3.5 ml. of ethyl acetate in the presence of 1.5 ml. of lithium hydroxide. The solution formed is mixed with a solution of 0.5 g. of spermacetic Wax in 3 ml. of ethyl acetate and the resulting solution of wax was incorporated into a blue-sensitive silver halide emulsion together with stearic acid and Spermafol 52 (trade name) as waxes instead of spermacetic wax.

EXAMPLE 19 1 g. of magenta-forming colour coupler having the following structural formula:

mo o-NHC o and 0.5 g. of the mask-forming agent having the following structural formula:

and 0.5 g. of SES2,T1 (trade name for sucrose distearate) are dissolved in a mixture of 5.5 ml. of ethyl acetate and 1 ml. of ethanol in the presence of 0.5 ml. of polyethylene glycol oleate.

The solution formed is dispersed by means of an ultrasonic wave generator into 30 ml. of a 5% aqueous solution of gelatin, containing 0.5 ml. of dodecylbenzene sulphonic acid sodium salt.

The ethyl acetate is removed from the gelatin composition by evaporation under reduced pressure at 60 C.

In order to neutralize the sulphonic acid group of the colour coupler and to adjust the pH to 6 some 2 N sodium hydroxide was added to the gelatin composition whereupon the latter was admixed at 38 C. with g. of a green-sensitized silver bromoiodide emulsion (2.3 mole percent of iodide).

After addition of the necessary stabilizing, hardening and wetting agents the emulsion is coated on a support and dried in the usual way.

After exposure through a grey wedge with constant 0.15 the photographic material is developed for 9 minutes at 20 C. in a colour developing bath of the following composition:

G. Sodium hexametaphosphate 2 N,N-diethyl-p-phenylene diamine hydrochloride 3 Sodium sulphite 4 Sodium carbonate 57 Hydroxylamine hydrochloride 1.5 Potassium bromide 1 Water to 1000 cc. (pH=10.6).

This material is rinsed for 30 minutes at 18 to 20 C. and fixed for 5 minutes at 20 C. in a fixing bath of the following composition:

Sodium thiosulphate 200 Sodium bisulphite 25 Potassium alum 20 Equimolar mixture of acetic acid and sodium acetate 20 Boric acid 7.5

Water to 1000 cc. (pH=4).

Next, the material is rinsed again for 10 minutes at 18 to 20 C. and treated for 5 minutes in a bleaching bath of the following composition:

G. Potassium hexacyanoferrate (III) Potassium bromide 15 Borax 20 Magnesium sulphate 20 Water to 1000 cc. (pH=8.6).

Rinsing is continued for another 10 minutes at 18 to 20 C. and then the material is fixed again for 5 minutes at 20 C. in a bath of the following composition:

G. Sodium thiosulphate Sodium salt of ethylenediamine tetraacetic acid 1 Sodium carbonate (anhydrous) 6 Sodium bicarbonate 14 Sodium sulphite (anhydrous) 10 Water to 1000 cc. (pH=8.8).

Finally rinsing is continued for 10 minutes at 1 8 to 20 C. and the material is dried.

A primary magenta dye image as Well as a secondary yellow mask image of opposite gradation to the said primary dye image are formed.

In a similar way as described above, the colour coupler and mask former were incorporated into a silver halide emulsion and then processed to produce a magenta dye image and yellow mask image using however as waxes instead of SES-2, T1 (trade name), Japan wax and stearic acid.

EXAMPLE 20 1 g. of the cyano-forming colour coupler of Example 15 and 0.5 g. of stearic acid are dissolved in 5 m1. of dimethyl sulphoxide whereupon the solution obtained was dispersed by means of a high speed mixer in 10 m1. of a 5% aqueous gelatin solution comprising 0.5 ml. of a 25% aqueous solution of dodecylbenzcne sulphonic acid sodium salt.

The dimethyl sulphoxide is removed from the gelatin composition by washing with cold water the gelled and noodled composition. The noodles are remelted at 40 C. and the melt added in the dark to a red-sensitized silver halide emulsion. The emulsion is coated in the usual manner and dried.

Upon exposure and colour processing a cyan dye image is formed.

EXAMPLE 21 A light-sensitive colour material designated material A is prepared as follows:

117 g. of a red-sensitized silver bromoiodide emulsion (2.3 mole percent of iodide), which comprises per 1 g. an amount of silver halide equivalent to 47 g. of silver nitrate and 73.4 g. of gelatin, are diluted with 192.5 g. of a 7.5% aqueous solution of gelatin and 200 g. of distilled water. To the emulsion obtained is added a gelatin gel comprising a dispersion of colour coupler having the following structural formula:

11 we ONH Y Cl prepared by admixing by means of an ultrasonic wave generator a solution of 0.006 mole of said colour coupler in 14 ml. of ethyl acetate with 100 ml. of a 5% solution of gelatin and removing the ethyl acetate by evaporation under reduced pressure. After addition of the common additives such as stabilizers, wetting agents and hardeners the necessary amount of distilled water is added to obtain 575 g.

The emulsion obtained is coated on a cellulose triaoetate support pro rata of 125 g. per sq. in. The emulsion layer is dried and overcoated with a gelatin antistress layer.

A series of light-sensitive colour materials B, C, D, E. F, G and H were prepared in a similar way as material A with the difference however that the colour coupler is incorporated in the light-sensitive emulsion together with a wax. For this purpose the gelatin gel, which is admixed with the red-sensitized emulsion, is prepared by dispersing a solution of 0.006 mole of the colour coupler and 2 g. of a wax selected from: Span 60 (trade name), Spermafol 52 (trade name), vaselin, paraffin l36138, Japan wax, stearic acid, SES2, T-1 (trade name) in 20 ml. of ethyl acetate, in 100 ml. of a 5% solution of gelatin, and removing the ethyl acetate by evaporation under reduced pressure.

Material A comprising no wax in association with the colour coupler and materials B-H comprising colour coupler and wax, are exposed for & sec. through a step wedge with constant 0.30 and then developed for 8 min. at 20 C. in a developing bath of the following composition:

Water to make 1 litre.

The developed materials are treated for 2 min. at 18- 20 C. in an intermediate bath comprising 30 g. of sodium sulphate in 1 litre of water.

The materials are rinsed for 15 min. with water and treated in a bleach bath of the following composition:

G. Borax 20 Anhydrous potassium bromide 1'5 Anhydrous sodium bisulphate 4.2 Potassium hevacyanoferrate (HI) 100 Water to make 1 litre.

After bleaching the materials are rinsed with water for 5 min. and fixed in an aqueous solution of 200 g. of sodium thiosulphate per litre.

After a final rinsing for 15 min. the materials are dried.

Cyan wedge-images are obtained having the following absorption maxima:

Material A: 672 nm. material B: 674 nm. (max. material C: 566 mn. (max. material D: 666 nm. (max. material E: 566 nm. (max. material F: 658 nm. (max material G: 674 nm. (max. material H: 672 nm. (max.

(max. 1.85) 2.36) 1.60)

density: density: density: density: density: 1.42) density: 1.24) density: 2.59) density: 1.42)

From these results it appears that some waxes cause a marked shift of the absorption maximum to the shorter wavelengths, and also that with some waxes high maximum densities are obtained.

EXAMPLE 22 1 g. of the colour coupler of Example 21 is dissolved in 8 ml. of ethanol in the presence of 2 ml. of 1 N alcoholic potassium hydroxide.

The alkaline solution formed is admixed with 20 ml. of a 5% aqueous solution of gelatin and neutralized by means of 2 ml. of succinic acid.

The dispersion of colour coupler in aqueous gelatin in then dispersed in a solution of 0.5 g. of stearic acid in 45 ml. of ethyl acetate.

The liquid composition formed is dispersed by means of a high speed stirrer in 120 ml. of a 5% aqueous gelatin solution comprising 0.5 ml. of a 25% aqueous solution of dodecylbenzene sulphonic acid sodium salt.

The ethyl acetate is removed from the gelatin composition by evaporation under reduced pressure of 400 mm. Hg at a temperature of 60 C.

The composition from 'which the ethyl acetate has been removed is then admixed at 38 C. with 45 g. of a redsensitized silver halide emulsion whereupon the emulsion is coated and dried in the usual way.

Upon exposure through a step wedge and colour processing in the conventional way an intense cyan wedge image is formed.

EXAMPLE 23 1 g. of the magenta forming colour coupler of Example 4 is dissolved in 12 ml. of water and 4 ml. of ethanol.

The aqueous solution obtained is dispersed into a solution of 0.5 g. of Glycowax S 932 (trade name) in 25 ml. of ethyl acetate.

The liquid composition formed is dispersed by means of an ultrasonic wave generator into ml. of a 5% aqueous gelatin solution comprising 0.5 ml. of a 25% aqueous solution of dodecylbenzene-sulphonic acid sodium salt.

The ethyl acetate is removed from the gelatin com position by evaporation under reduced pressure at 60 C.

The gelatin composition is then admixed with a greensensitized silver halide emulsion and the emulsion coated and dried in the usual way.

Upon exposure and colour development a magenta dye image is formed.

EXAMPLE 24 1 g. of the magenta-forming colour coupler having the following structural formula:

is dissolved in 3 ml. of ethyl acetate at 65-70 C. To the solution formed 0.25 g. of beeswax is added whereupon the solution is dispersed by means of an ultrasonic wave generator into 16 ml. of a 5% aqueous solution of gelatin in the presence of 0.25 ml. of a 25 aqueous solution of dodecylbenzene sulphonic acid sodium salt as dispersing agent.

The ethyl acetate is removed from the dispersion by applying a vacuum of 300-400 mm. Hg at a temperature of 5560 C.

The resulting gelatin composition can be admixed with a green-sensitized silver halide emulsion as described in Example 17.

EXAMPLE 25 7.5 g. of the magenta-forming colour coupler of Example 19 are dissolved at 70 C. in a mixture of 37.5 ml.

of ethyl acetate, 12.5 ml. of polyethylene glycol oleate and 1.5 g. of beeswax.

The solution formed is dispersed by means of a speed mixer into 225 ml. of a 3% aqueous solution of gelatin in the presence of 4 ml. of a 25% aqueous solution of dodecylbenzene sulphonic acid sodium salt and 6.5 ml. of 1 N sodium hydroxide.

By the presence of the alkali the pH of the gelatin solution is adjusted so that flocculation of the gelatin is avoided.

The ethyl acetate is removed from the gelatin composition by evaporation at 60-65 C. under a reduced pressure of 250-300 mm. Hg.

The gelatin-composition is then admixed at 38 C. with a conventional green-sensitized silver halide emulsion whereupon the latter is coated and dried in the usual way.

Upon exposure through a step wedge and colour processing in the conventional Way an intense magenta coloured wedge image is formed.

We claim:

1. A hydrophilic colloid composition comprising a continuous phase containing a hydrophilic colloid and a dispersed phase uniformly distributed through said continuous phase of a color-coupling or mask-forming compound in contact with a water-insoluble chemically inert wax distinct from said color-coupling or mask-forming compound.

2. A hydrophilic colloid composition as in claim 1 wherein said dispersed phase comprises particles of a water-insoluble chemically inert wax containing a color coupling and/or mask-forming compound distinct from said wax.

3. A hydrophilic colloid composition according to claim 2, wherein said composition is a photographic light-sensitive silver halide colloid emulsion comprising a separate disperse phase of silver halide in said hydrophilic colloid.

4. A hydrophilic colloid composition according to claim 2, wherein said hydrophilic colloid is gelatin.

5. A hydrophilic colloid composition according to claim 2, wherein said water-insoluble chemically inert wax is a natural Wax selected from animal Waxes, insect Waxes, vegetable waxes, mineral waxes or petroleum waxes.

6. A hydrophilic colloid composition according to claim 2, wherein said water-insoluble chemically inert wax is a synthetic wax selected from the group consisting of:

long-chain hydrocarbons and halogenated and partly oxidized long-chain hydrocarbons,

Wax-like saturated and unbranched fatty acids and alcohols,

esters of fatty acids and fatty alcohols,

pentaerythritol esters of fatty acids,

alkyl esters of 12-hydroxy stearic acid,

sucrose diesters of fatty acids,

esters of fatty acids and sorbitol,

hydrogenated castor oil or sperm oil,

amide derivatives of fatty acids.

References Cited UNITED STATES PATENTS 2,239,704 4/1941 De Boer et al. 9649 2,269,158 l/ 1942 Martinez 9674 2,500,052 3/1950 Yackel 96 36 FOREIGN PATENTS 680,937 2/1964 Canada 96100 ROBERT F. BURNETT, Primary Examiner R. A. DAWSON, Assistant Examiner i US. Cl. X.R. 

